I am reproducing iron oxide nanoparticles from "Ultra-Large-Scale Syntheses of Monodisperse Nanocrystals." hyun et. al
in this process nanoparticles were made from iron oleate complex with solvent 1-octadecene at 320 degree.
I succeeded made nanoparticles but failed washing process.
as mentioned in papaer, after reaction, I put excess ethanol in to reaction mixture. and centrifuge and put under high vacuum for an hour.
but even they were under high vacuum for long time, some viscous liquid remained in nanoparticles.
so i tried to wash it with ethylacete or ethanol and dried.
and i found particles didn't be dispersed anymore in nonpolar solvent(hexane, chloroform), which were dispersed well before drying.
I really want to know what is the reason why i failed to dry particles.
please let me know about "washing process" in paper"Ultra-Large-Scale Syntheses of Monodisperse Nanocrystals" if you have experience.
thanks very much
Your clues and keys are found in the statements 'i found particles didn't be dispersed anymore in nonpolar solvent(hexane, chloroform), which were dispersed well before drying' and 'i failed to dry particles'. I'll start with 2 quotations:
Rudy Rucker: 'I think that dry nanotechnology is a dead end'
Jim Adair: 'If the particles are agglomerated and sub-micron it may be impossible to adequately disperse the particles……'The energy barrier to re-dispersion is greater if the particles have been dried. Therefore the primary particles must remain dispersed in water….' J H Adair, E. Suvaci, J Sindel, “Surface and Colloid Chemistry” Encyclopedia of materials: Science and Technology pp 8996 - 9006 Elsevier Science Ltd. 2001 ISBN 0-08-0431526
Then take a look at:
Nov 11th, 2008. Dispersion and nanotechnology http://tinyurl.com/hpywsge
November 3rd, 2015 Adhesion and cohesion http://tinyurl.com/zwb2wlh
Sept 17th, 2007 Nanomaterials & dispersion issues
http://www.brainshark.com/brainshark/vu/view.asp?pi=522875626&text=M021507
Hi,
I would sugesst another washing procedure. Add chloroform instead of ethanol after cooling the reaction mixture to room temperature. Then precipitate NPs by adding aceton and again redisperse them in chloroform. Repeat this procedure 2-3 times and finally disperse NPs in chloroform. This works for me perfectly for years. after having a highly stable nps suspension, if you dry them at moderate temperature like 40°C, you will be able to once again redisperse them in non-polar solvent. However, the yield will be may around 60-70 % on a lucky day. typically one woud aviod drying colloidal nps since all the required surface modifications are done in liquid state. So, there is no real need to do any drying except some physical analyses.
thank you so much Aidin Lak
your answer was so much good information to me.
but one thing, the reason why i tried to dry nps is to weigh the particles for the precise weight measured surface modification. do you have experiment that you fully dried nps to make them solid form?
I always dry only a very small sample for weight content and XRD. Centrifugation, dialysis or phase transfer (polar to no polar medium) can be performed.
Drying will reduce the accessible surface as Alan suggested.
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